Handling guilt and grief?

My grandma passed two-ish months ago I believe, the last ever conversation i had is when I was irritated, she asked me to pour her a cup of coffee but I did it anyway cause I felt guilty to get upset of something so small. She thanked me, I said your welcome nana, and I went back to sitting on the couch beside her.

I shouldn’t have excuses but the reason I was irritated is because my aunt ditched, leaving me to babysit her two toddlers by force. It’s not new, shes been doing this since her youngest was born (2), usually leaving me to look after them when she leaves. My aunt is an addict. I love my aunt then “hate” her.

After my nana passed, things went downhill for me—I dealt with depression since 12. Got out of it at 16, now it’s back and I’m 18. Failing school and still in 10th grade, don’t feel like going back cause of shame. But there are moments where I get up, do a few things like cooking myself something small to eat or change my little cousins diapers, or clean/make their bottles.